Entanglement Control of Azobenzene by Photoisomerization in NMR Quantum Computer

TL;DR

This paper explores how photoisomerization of azobenzene can be used to control entanglement in NMR quantum computers by altering molecular structure and spin-spin coupling, demonstrated through ab initio calculations and NMR spectra analysis.

Contribution

It introduces a method to manipulate qubit entanglement via photoisomerization in azobenzene, linking molecular structural changes to quantum entanglement control.

Findings

Significant change in coupling strength between nuclei upon isomerization

Accurate reproduction of experimental NMR chemical shifts

Potential for photo-controlled quantum entanglement manipulation

Abstract

Entanglement control of qubits in a photoisomerizing molecule is studied in the context of an NMR quantum computer by taking azobenzene as an example. Azobenzene has two different isomers, {\it{}trans}-azobenzene (TAB) and {\it{}cis}-azobenzene (CAB), which can be interconverted by photoisomerization. Changing molecular structure leads to change in the spin-spin coupling constant, and hence leads to change in entangling operation time. We first obtain stable structures of TAB and CAB by {\it ab initio} calculation. Then, we calculate the NMR spectra of these isomers and verify that they reproduce the chemical shift obtained experimentally with a good precision. Our result indicates that the coupling strength between a $^{15}$N and a $^{13}$C nuclei in the molecule changes by a large amount under photoisomerization.